JP6098764B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus in which a steering assist force by a motor is applied to a steering system of a vehicle, and in particular, the steering angle and vehicle information are not affected by variations in manufacturing of the vehicle and the steering system, aging, etc. The present invention relates to an electric power steering apparatus capable of realizing a desired steering torque according to the above.

  An electric power steering apparatus (EPS) that assists the steering system of a vehicle with the rotational force of a motor is a steering assist force applied to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a reduction gear. Is supposed to be granted. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist control torque. In feedback control, the motor applied voltage is adjusted so that the difference between the steering assist command value (current command value) and the motor current detection value becomes small. -Adjusting tees.

  The general configuration of the electric power steering apparatus will be described with reference to FIG. 6b is further connected to the steering wheels 8L and 8R via hub units 7a and 7b. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1 as the torsion torque of the torsion bar, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft via the reduction gear 3. 2 is connected. The control unit (ECU) 30 that controls the electric power steering apparatus is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11. The control unit 30 calculates a current command value serving as an assist command based on the steering torque Th detected by the torque sensor 10 and the vehicle speed Vel detected by the vehicle speed sensor 12, and compensates for the calculated current command value. The current supplied to the motor 20 is controlled by the voltage control value Vref subjected to the above. The steering angle sensor 14 for detecting the steering angle is not essential and may not be provided, and may be obtained from a rotation sensor such as a resolver connected to the motor 20.

  The control unit 30 is connected to a CAN (Controller Area Network) 40 that exchanges various types of vehicle information, and the vehicle speed Vel can also be received from the CAN 40. The control unit 30 can be connected to a non-CAN 41 that exchanges communications, analog / digital signals, radio waves, and the like other than the CAN 40.

  In such an electric power steering apparatus, the control unit 30 is mainly composed of a CPU (including an MPU and MCU). General functions executed by a program inside the CPU are shown in FIG. The structure is

  The function and operation of the control unit 30 will be described with reference to FIG. 2. The steering torque Th from the torque sensor 10 and the vehicle speed Vel from the vehicle speed sensor 12 are input to the current command value calculation unit 31, and the current command value calculation unit 31. Calculates the current command value Iref1 using an assist map or the like based on the steering torque Th and the vehicle speed Vel. The calculated current command value Iref1 is added by the adding unit 32A and the compensation signal CM from the compensating unit 34 for improving the characteristics, and the added current command value Iref2 is limited to the maximum value by the current limiting unit 33. The current command value Irefm whose maximum value is limited is input to the subtraction unit 32B and subtracted from the motor current detection value Im.

  Deviation I (= Irefm−Im), which is a result of subtraction in subtraction unit 32B, is PI-controlled by PI (proportional integration) control unit 35, and voltage control value Vref subjected to PI control is input to PWM control unit 36, and carrier signal The duty is calculated in synchronization with the CF, and the motor 20 is PWM driven via the inverter 37 with a PWM signal. The motor current value Im of the motor 20 is detected by the motor current detector 38, and is input to the subtraction unit 32B and fed back.

  The compensation unit 34 adds the detected or estimated self-aligning torque (SAT) 343 to the inertia compensation value 342 by the addition unit 344, and further adds the convergence control value 341 to the addition result by the addition unit 345. The addition result is input as a compensation signal CM to the adding unit 32A, and the characteristics of the current command value are improved.

  As described above, in the assist control by the conventional electric power steering apparatus, the steering torque applied by the driver's manual input is detected by the torque sensor as the torsional torque of the torsion bar, and the feedforward is mainly performed according to the steering torque. The current command value for assist control is set. For this reason, it is difficult to maintain the same level of steering performance due to variations in manufacturing of the vehicle and the steering system, aging of the vehicle and the steering system, and the like.

  Japanese Patent No. 5208894 (Patent Document 1) has been proposed as a vehicle control apparatus that solves this problem. The vehicle control device disclosed in Patent Document 1 includes a steering angle detecting unit that detects a steering angle of a steering by a driver and a steering angle or a steering when the steering is steered without switching the steering direction from the neutral state of the steering. The amount of response of the driver obtained based on the sense amount of the change rate of the steering torque with respect to the change of the steering angle and the sense amount of the steering torque is constant within a range where the steering torque is less than the predetermined value, and Detected based on a predetermined relationship between the steering angle or steering torque and the response amount, where the response amount monotonously increases as the steering angle or steering torque increases within a range where the steering angle or steering torque is equal to or greater than a predetermined value. Target setting means for setting the steering torque corresponding to the steering angle as a target value, and the target value of the steering torque set by the target setting means is realized A vehicle control device and a control for controlling means as.

Japanese Patent No. 5208894

  In the apparatus described in Patent Document 1, a deviation between the target value of the steering torque (torsion angle) and the detected steering torque (torsion angle) is obtained, and PI (proportional integration) control is performed on the deviation, The target value of steering torque is realized. As a result, the amount of friction of the motor and the steering mechanism system changes due to variations in manufacturing of the vehicle and the steering system, aging, etc., and the followability to the target steering torque is affected.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to follow the column angle to a value corresponding to the steering angle and vehicle information (vehicle speed, yaw rate, lateral acceleration (lateral G), etc.). It is an object of the present invention to provide an electric power steering device that realizes a desired steering feeling by being controlled so as to be unaffected by variations in manufacturing of vehicles and steering systems, aging, and the like.

The present invention relates to an electric power steering device configured to assist control of a steering system by calculating a current command value based on at least a steering angle and driving a motor based on the current command value. The above-described object is to provide a target column angle calculation unit that calculates a target column angle based on the steering angle and vehicle information, and a column angle control that calculates the current command value based on the target column angle and the detected actual column angle. A target column angular velocity calculator that calculates a target column angular velocity based on a difference between the target column angle and the actual column angle, and an actual column angular velocity based on the actual column angle. And a speed control unit that calculates the current command value based on the target column angular velocity and the actual column angular velocity. A control unit, a third subtraction unit that obtains a speed difference between the target column angular velocity and the actual column angular velocity; an integration unit that integrates the velocity difference and multiplies an integral gain; and a proportional that multiplies the actual column angular velocity by a proportional gain. and a control unit, wherein the output of the integrator by subtracting the output of the proportional controller is composed of the fourth subtracting unit for obtaining the current command value, the actual column angle to the steering angle and the vehicle information This is achieved by controlling the angle to a corresponding value. In addition, the object of the present invention is to calculate a target column angle based on the steering angle and vehicle information, and to calculate the current command value based on the target column angle and the detected actual column angle. A column angle control unit that performs a target column angular velocity calculation unit that calculates a target column angular velocity based on a difference between the target column angle and the actual column angle, and based on the actual column angle. A differential unit that calculates an actual column angular velocity, and a speed control unit that calculates the current command value based on the target column angular velocity and the actual column angular velocity, and the target column angular velocity calculating unit includes the target column angular velocity. A second subtracting unit that calculates an angular difference between the column angle and the actual column angle, and a position control unit that calculates the target column angular velocity by multiplying the angular difference by a proportionality constant. The speed control unit includes a third subtraction unit that calculates a speed difference between the target column angular velocity and the actual column angular velocity, an integration unit that integrates the speed difference and multiplies an integral gain, and multiplies the actual column angular velocity by a proportional gain. And a fourth subtraction unit that subtracts the output of the proportional control unit from the output of the integration unit to obtain the current command value, and determines the actual column angle as the steering angle and the vehicle. This is achieved by controlling the angle to a value according to information. Furthermore, the object of the present invention is to provide a limiter that outputs the current command value when the vehicle information is at least vehicle speed, yaw rate, lateral acceleration, or restricts the upper and lower limit values of the output of the speed controller. By being added, it is achieved more effectively.

In addition, the object of the present invention is to calculate a target column angle based on the steering angle and vehicle information, and to calculate the current command value based on the target column angle and the detected actual column angle. A column angle control unit that performs a target column angular velocity calculation unit that calculates a target column angular velocity based on a difference between the target column angle and the actual column angle, and based on the actual column angle. A differential unit that calculates the actual column angular velocity, a speed feedforward control unit that performs speed feedforward control of the target column angle, and a speed feedforward control value from the speed feedforward control unit is added to the target column angular speed. Based on the final target column angular velocity and the actual column angular velocity, an adder for obtaining a final target column angular velocity, and the current command value Is composed of a speed control unit for calculating, is achieved by which is the actual column angle such that the angle control to a value corresponding to the steering angle and the vehicle information. Further, the vehicle information includes at least three of vehicle speed, yaw rate, and lateral acceleration, or the target column angle calculation unit sets a desired steering torque according to the steering angle; and A dividing unit that calculates a target twist angle by dividing the desired steering torque by a spring constant of a torsion bar and a first subtracting unit that subtracts the target twist angle from the steering angle; or This is achieved more effectively by adding a limiter that outputs the current command value by limiting the upper and lower limit values of the output of the speed control unit.

  According to the electric power steering apparatus of the present invention, a desired steering torque is realized by controlling the column angle so as to follow a value corresponding to the steering angle and vehicle information (vehicle speed, yaw rate, lateral acceleration, etc.). doing. In addition, because the angle is controlled according to the deviation between the target column angle to achieve the desired steering torque and the detected actual column angle, it affects the manufacturing variations and aging of the vehicle and steering system. Instead, the same level of steering performance can be maintained.

It is a lineblock diagram showing an outline of an electric power steering device. It is a block diagram which shows the structural example of the control system of an electric power steering apparatus. It is a block diagram which shows the structural example of this invention. It is a block diagram which shows the structural example of a target column angle calculating part. It is a block diagram which shows the structural example of a column angle control part. It is a flowchart which shows the example of whole operation | movement of this invention. It is a flowchart which shows the operation example of a column angle control part. It is a block diagram which shows the other structural example of a column angle control part. It is a characteristic view explaining the effect of the present invention. It is a characteristic view explaining the effect of the present invention.

  The electric power steering device of the present invention is not affected by variations in manufacturing of vehicles and steering systems, aging, etc., and realizes a desired steering torque according to the steering angle and vehicle information. A target column angle calculation unit that calculates a target column angle based on the target column angle, and a column angle control unit that calculates a current command value based on the target column angle and the detected actual column angle. The angle is controlled to a value according to the information.

  Thereby, it is possible to maintain the same level of steering performance without being affected by variations in manufacturing of the vehicle and the steering system, aging, and the like.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 3 shows an example of an embodiment of the present invention. The steering angle θh, which is the steering wheel angle on the steering wheel side with respect to the torsion bar, is input to the target column angle calculation unit 110, and the vehicle speed, yaw rate, lateral acceleration, etc. Information VI is also input to the target column angle calculation unit 110. The target column angle θref calculated by the target column angle calculation unit 110 is input to the column angle control unit 120, and the EPS steering system 100 is driven and controlled by the current command value Iref calculated by the column angle control unit 120. The column angle control unit 120 calculates a current command value Iref such that the column angle follows the target column angle θref. Further, the EPS steering system 100 is provided with a sensor for detecting a column angle that is a column side angle with respect to the torsion bar, and the detected actual column angle θ is input to the column angle control unit 120. .

  For example, the target column angle calculation unit 110 is configured as shown in FIG. That is, the steering angle θh is input to the steering torque setting unit 111 and the subtraction unit 113, and the steering torque setting unit 111 outputs a desired steering torque according to the steering angle θh according to a predetermined function. The desired steering torque is divided by the spring constant Kt of the torsion bar in the dividing unit 112, and the target twist angle Δθref as a result of the division is subtracted and input to the subtracting unit 113. The subtraction unit 113 subtracts the target torsion angle Δθref from the steering angle θh, and outputs the target column angle θref (= θh−Δθref) as the subtraction result.

  The target column angle θref calculated by the target column angle calculation unit 110 in this way is input to the column angle control unit 120. The actual column angle θ is also input to the column angle control unit 120.

  The column angle control unit 120 is configured as shown in FIG. 5, for example. That is, the target column angle θref is added to the subtractor 121 and the actual column angle θ is subtracted to the subtractor 121 and input to the differentiator 123 that performs time differentiation. The angle difference (= θref−θ) calculated by the subtraction unit 121 is input to the position control unit 122 and multiplied by a proportional constant Kpp to calculate the target column angular velocity ω2. The subtraction unit 121 and the position control unit 122 constitute a target column angular velocity calculation unit.

  The target column angular velocity ω2 is added and input to the subtracting unit 131 in the speed control unit 130 that performs the IP control. Further, the actual column angular velocity ω 1 calculated by the differentiating unit 123 is subtracted and input to the subtracting unit 131 in the speed control unit 130 and also input to the proportional control unit 133. The subtraction result (= ω2−ω1) of the subtraction unit 131 is input to the integration unit 132, integrated, and multiplied by the integration gain Kvi, and the integration result SC1 is added to the subtraction unit 134. Further, the proportional control result SC2 of the proportional control unit 133 is subtracted and input to the subtracting unit 134, and the current command value Ir (= SC1-SC2), which is the subtraction result of the subtracting unit 134, is limited in upper and lower limit values by the limiter 124. A current command value Iref is output. The speed control unit 130 calculates a current command value Ir such that the actual column angular speed ω1 follows the target column angular speed ω2.

  In such a configuration, an example of the overall operation will be described with reference to the flowchart of FIG.

  First, the steering angle θh and the vehicle information VI are input (step S10), and the target column angle calculation unit 110 calculates the target column angle θref (step S20). The target column angle θref is input to the column angle control unit 120, and the actual column angle θ from the EPS steering system 100 is also input to the column angle control unit 120 (step S30). The column angle control unit 120 performs angle control based on the target column angle θref and the actual column angle θ (step S40), drives and controls the EPS steering system 100 with the current command value Iref obtained by calculation (step S70), and ends. The above operation is repeated until it becomes (step S71).

  FIG. 7 shows an example of the operation of the column angle control unit 120. First, the target column angle θref and the actual column angle θ are input (step S41), and the angle difference (= θref−θ) is calculated by the subtraction unit 121. The actual column angle θ is input to the position controller 122, and the actual column angle θ is input to the differentiator 123 (step S42). The position control unit 122 calculates the target column angular velocity ω2 based on the angle difference (step S43), and the differentiation unit 123 calculates the actual column angular velocity ω1 by time differentiation (step S44).

  The target column angular velocity ω2 and the actual column angular velocity ω1 are input to the subtractor 131, and the angular velocity difference (= ω2-ω1) is calculated (step S45). The calculated angular velocity difference is input to the integration unit 132 and subjected to integration control (step S46), and the actual column angular velocity ω1 is input to the proportional control unit 133 and proportionally controlled (step S47). The integration result SC1 and the proportional control result SC2 are input to the subtraction unit 134 to calculate the difference (= SC1-SC2) (step S48), and the difference is output as the current command value Ir. The current command value Iref is output (step S51).

  FIG. 8 shows another configuration example of the column angle control unit 120, and a speed feedforward control unit 140 that multiplies the differential value of the target column angle θref by the gain Kvf and adds it to the target column angular speed ω2. A value added to the target column angular velocity ω 2 is set as a final target column angular velocity ω 3, and the final target column angular velocity ω 3 is input to the speed control unit 130. The speed feedforward control unit 140 improves the followability (immediate response) of the column angle θ with respect to the target column angle θref.

  For example, in the first embodiment, a target column angle θref that provides a desired steering torque according to the steering angle θh is output from the target column angle table, and the current for causing the column angle θ to follow the target column angle θref by angle control. Calculate the command value. When the steering angle θh is moved as shown in FIG. 9A, a target column angle θref for realizing a desired steering torque is calculated, and the column angle θ follows this. As a result, the actual twist angle Δθ becomes a thin line with respect to the desired twist angle Δθref (thick line) shown in FIG. 9B. In FIG. 9B, the difference between the desired twist angle Δθref (thick line) and the actual twist angle Δθ (thin line) is a slight difference, and is the same in a region where the steering angle θh does not vary. As a result, the steering torque appearing in the hand feeling is as shown in FIG. 9C (desired steering torque is omitted).

  In order to improve the followability to the target column angle θref, a value obtained by multiplying the target column angular velocity ω2 shown in the first embodiment by a gain corresponding to the differential value of the target column angle θref is added (speed feed). Forward control), the final target column angular velocity ω3 may be used. The simulation result of the second embodiment is shown in FIG. FIG. 10A shows a change in the steering angle θh. In FIG. 10B, the second embodiment (broken line) is more effective than the twist angle Δθ (thin line) in the first embodiment with respect to the desired twist angle Δθref (thick line). ) Follows the desired twist angle Δθref. In FIG. 10B, the desired torsion angle Δθref (thick line) and the actual torsion angle Δθ (dashed line) almost overlap each other, and the desired torsion angle Δθref (thick line) does not vary in the steering angle θh. ), The twist angle Δθ (thin line) in the first embodiment and the desired twist angle Δθref (broken line) in the second embodiment are the same. The steering torque that appears in the hand feeling is as shown in FIG.

  In addition, in order to suppress the influence by SAT disturbance, you may add to the electric current command value of angle control in the direction which suppresses the electric current command value of SAT estimated value. Further, the speed control unit is not limited to the above-described IP control, and for example, PI control, P control, PID control, and PI-D control may be used.

  Further, when there is no angle sensor for detecting the column angle, the torsion bar torsion angle (for torque detection) is subtracted from the steering angle (steering wheel angle) to obtain “column angle = steering angle−torsion angle”. Also good.

1 Handle 2 Column shaft (steering shaft, handle shaft)
DESCRIPTION OF SYMBOLS 10 Torque sensor 12 Vehicle speed sensor 13 Battery 20 Motor 100 EPS Steering system 110 Target column angle calculation part 111 Steering torque setting part 120 Column angle control part 122 Position control part 123 Differentiation part 124 Limiter 130 Speed control part 140 Speed feedforward control part

Claims (8)

In the electric power steering apparatus configured to assist the steering system by calculating a current command value based on at least a steering angle and driving a motor based on the current command value,
A target column angle calculation unit that calculates a target column angle based on the steering angle and vehicle information; and a column angle control unit that calculates the current command value based on the target column angle and the detected actual column angle. ,
The column angle control unit is
A target column angular velocity calculation unit that calculates a target column angular velocity based on the difference between the target column angle and the actual column angle, a differentiation unit that calculates an actual column angular velocity based on the actual column angle, the target column angular velocity and the A speed control unit that calculates the current command value based on the actual column angular velocity,
The speed controller is
A third subtraction unit for obtaining a speed difference between the target column angular velocity and the actual column angular velocity; an integration unit that integrates the speed difference and multiplies an integral gain; and a proportional control unit that multiplies the actual column angular velocity by a proportional gain; It said being an output of the integrator by subtracting the output of the proportional controller and a fourth subtracting unit for obtaining the current command value,
An electric power steering apparatus characterized in that the actual column angle is controlled to a value corresponding to the steering angle and the vehicle information. In the electric power steering apparatus configured to assist the steering system by calculating a current command value based on at least a steering angle and driving a motor based on the current command value,
A target column angle calculation unit that calculates a target column angle based on the steering angle and vehicle information; and a column angle control unit that calculates the current command value based on the target column angle and the detected actual column angle. ,
The column angle control unit is
A target column angular velocity calculation unit that calculates a target column angular velocity based on the difference between the target column angle and the actual column angle, a differentiation unit that calculates an actual column angular velocity based on the actual column angle, the target column angular velocity and the A speed control unit that calculates the current command value based on the actual column angular velocity,
The target column angular velocity calculation unit is
A second subtracting unit that calculates an angle difference between the target column angle and the actual column angle, and a position control unit that calculates the target column angular velocity by multiplying the angular difference by a proportional constant,
The speed controller is
A third subtraction unit for obtaining a speed difference between the target column angular velocity and the actual column angular velocity; an integration unit that integrates the speed difference and multiplies an integral gain; and a proportional control unit that multiplies the actual column angular velocity by a proportional gain; A fourth subtraction unit that subtracts the output of the proportional control unit from the output of the integration unit to obtain the current command value;
An electric power steering apparatus characterized in that the actual column angle is controlled to a value corresponding to the steering angle and the vehicle information. The electric power steering apparatus according to claim 1 or 2, wherein the vehicle information includes at least three of a vehicle speed, a yaw rate, and a lateral acceleration. The electric power steering device according to any one of claims 1 to 3, further comprising a limiter for limiting the upper and lower limit values of the output of the speed control unit and outputting the current command value. In the electric power steering apparatus configured to assist the steering system by calculating a current command value based on at least a steering angle and driving a motor based on the current command value,
A target column angle calculation unit that calculates a target column angle based on the steering angle and vehicle information; and a column angle control unit that calculates the current command value based on the target column angle and the detected actual column angle. ,
The column angle control unit is
A target column angular velocity calculating unit that calculates a target column angular velocity based on the difference between the target column angle and the actual column angle, a differentiating unit that calculates an actual column angular velocity based on the actual column angle, A speed feedforward control unit that performs feedforward control, an addition unit that obtains a final target column angular velocity by adding a speed feedforward control value from the speed feedforward control unit to the target column angular velocity, the final target column angular velocity and the A speed control unit that calculates the current command value based on the actual column angular velocity,
An electric power steering apparatus characterized in that the actual column angle is controlled to a value corresponding to the steering angle and the vehicle information. The electric power steering apparatus according to claim 5, wherein the vehicle information includes at least three of a vehicle speed, a yaw rate, and a lateral acceleration. The target column angle calculation unit is
A steering torque setting unit that sets a desired steering torque according to the steering angle, a division unit that calculates a target torsion angle by dividing the desired steering torque by a spring constant of a torsion bar, and the target from the steering angle The electric power steering apparatus according to claim 5, further comprising a first subtracting unit that subtracts a twist angle. The electric power steering device according to any one of claims 5 to 7, further comprising a limiter for limiting the upper and lower limit values of the output of the speed control unit and outputting the current command value.

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